Although the 2013 NFL Free Agency period is one month away and the market will be thinned at the top by franchise tags and contract extensions, this is a good time to survey the prospective field. The NFL Scouting Combine kicks off in less than two weeks, and it is in Indianapolis that free-agency scuttlebutt commences as player representatives meet face-to-face with team officials.

This is a free agency position ranking. As it stands, I believe cornerback to be the deepest, most talented group of players with expiring contracts. I think quarterback is the weakest, for an obvious reason: NFL teams simply don't let franchise signal callers hit the open market. Offensive tackle and defensive end look very strong. Inside linebacker and center are bereft of quality starters.

On the back page is my Free Agent Top 40 for the 2013 offseason. I did not include Joe Flacco or Ryan Clady, because neither of them is going anywhere. Tony Gonzalez's contract is up, but his future is murky at best and he is not included, either.

Restricted Free Agents are not considered here because they so rarely change teams.

Obviously past their primes, Sheldon Brown, 33, Quentin Jammer, 33, Terence Newman, 34, and Rashean Mathis, 32, each may have a year or two left as solid starting cornerbacks in the league. Brown, Jammer, and Mathis could potentially extend their careers by converting to safety.

Although former first-round pick Leodis McKelvin has not panned out as a cover corner, he is still only 27 and led the NFL in 2012 punt return average while bringing back two punts to the house.

Since the positions are valued differently inside the NFL, offensive tackles can be halved into left and right. Left tackles are the highest paid O-Line position. Right tackles are viewed as inferior, although the league's best running teams unfailingly field high-impact tackle play on the right side.

Albert, Long, Beatty, Bushrod, Baker, and Bryant McKinnie, 33, are the best left tackles free agency has to offer. Smith, Vollmer, Cherilus, and Loadholt are difference makers on the right side. Vollmer is especially intriguing because he possesses athleticism and length to play both tackle spots, and made five starts on Tom Brady's blindside as a rookie in 2009. If Vollmer hits free agency -- and the Patriots will probably make sure that he does not -- it's conceivable that interested teams would view him as a left tackle, setting up Vollmer for a monster pay day.

3. Defensive End

This year's free-agent defensive end class isn't quite as talent rich as the big names atop the list might indicate. But it's a reasonably solid group with, by my count, at least seven capable NFL starters.

Cliff Avril, 26, has 29 sacks and nine forced fumbles over the past three seasons. He's "scheme versatile," capable of fitting 3-4 defenses at outside linebacker and 4-3s as a hand-in-the-dirt end. Avril is the clear prize of this year's defensive end class. Michael Johnson, 26, isn't far off after a breakout, 11.5-sack season. Always oozing talent, Johnson has long faced questions about his motor, however, and it's red-flaggy that he put together a career year in a contract season. It makes him an ideal franchise-tag candidate for the Bengals. So perhaps he won't hit the market.

Versatile Michael Bennett, 27, is No. 3 in the defensive end rankings and can rush the passer from both tackle and left end. Bennett was a key contributor on Tampa's league-best run defense in 2012. Osi Umenyiora, 31, Dwight Freeney, 32, and Israel Idonije, 32, all have good football left but are past their primes. Matt Shaughnessy, 26, once looked like a future star in Oakland, but lost his passing-down role to early-season street free-agent pickup Andre Carter because Shaughnessy couldn't generate any pressure. He still may be the best value signing in this group.

The wide receiver free-agent eligibles fall off a cliff after the initial six or so players, but there is obvious star power at the top. Dwayne Bowe, 28, can take over games when focused, and he's never, ever played with a competent quarterback. Mike Wallace, 26, was considered the NFL's premier deep threat as recently as the 2012 offseason. Greg Jennings, 29, is a playmaker both in the slot and along the sidelines. Wes Welker, 31, is uncoverable between the numbers. Soo too is Danny Amendola, 27, at least when healthy. Brian Hartline, 26, was stretched as the Dolphins' No. 1 receiver in 2012, but is still coming off a breakout year.

There's a good chance you've never heard of Desmond Bryant, 27, but you need to get used to it. He's going to be a very hot free agent. I recall watching tape of offensive skill position players last offseason, and defensive end No. 90 for Oakland kept showing up. In 2012, Bryant kicked inside to replace injured Richard Seymour and graded out as Pro Football Focus' No. 6 overall defensive tackle. He was the best player on a bad defense. A Harvard alum with a scheme-versatile body (6'6/311), Bryant will appeal to 3-4 teams as a five-technique end and 4-3 clubs at interior tackle.

"Rush linebacker" is traditionally associated with 3-4 defenses. As the 3-4 becomes more and more prevalent, we need to consider "rush 'backer" its own position rather than grouping it in with defensive ends or outside linebackers.

Paul Kruger, 27, was the Super Bowl champions' best pass rusher for the duration of the 2012-2013 season and is arguably the premier prize of free agency. He's going to rake in a ton of money. Anthony Spencer, 29, was always a stud edge-setting run defender before breaking out with 11 sacks this past year. He outplayed future Hall of Famer DeMarcus Ware. Connor Barwin, 26, registered 11.5 sacks in 2011 before crashing back to Earth with three in 2012. Barwin is not an explosive outside-edge rush 'backer and is a candidate to get overpaid on the open market.

Shaun Phillips, 31, Antwan Barnes, 28, and Victor Butler, 25, round out the rush linebacker depth. Butler is intriguing. Buried behind Spencer and Ware the past four seasons, Butler still managed 11 sacks and four forced fumbles while starting just 1-of-63 games. He is a free-agent sleeper.

7. Safety

The safety class looks swell on paper, but I'm afraid it'll be thinned out by franchise tags and seemingly obvious re-signings. The franchise number for safeties is an affordable $6.798 million; only tight ends and kickers cost less to tag. I think we'll see top safety Jairus Byrd, 26, tagged and quite possibly William Moore, 27. The Niners also won't let Dashon Goldson, 28, get away.

Chung and Phillips might be the safeties to target for teams incapable of ponying up for what'll be an unwieldy price tag on Landry, Byrd, Moore, or Goldson. Chung and Phillips both possess Pro Bowl-caliber talent; only bad injury luck has diminished their market value. Since both are under 27 years old, it's quite possible Phillips and Chung would be amenable to one-year, prove-it deals.

8. Tight End

I have tight end ranked relatively low, but I think it's a quietly strong group. Especially when you include Texans fullback/H-back James Casey, 28, who demonstrates Hernandezian movement skills in pass routes but played out of position as a lead blocker in Gary Kubiak's offense. Casey needs to get out of Houston and find a chance to start. He can get open and has great hands.

Fred Davis, 27, is a field stretcher and underrated blocker if his Achilles' checks out. Dustin Keller, 28, has been held hostage statistically by putrid Jets offenses and needs to leave New York to maximize his god-given ability. Jared Cook, 25, is a freak of nature talent. Martellus Bennett, 25, is a terrific blocker and flashed taking his receiving game to a top-ten level when healthy in 2012.

This is where free agency begins to really thin out. The top get would be longtime Jaguars outside linebacker Daryl Smith, who can play strong side, weak side, or even man the middle. Smith, however, is going on age 31 and struggled in his only two 2012 appearances after returning from recurring groin problems.

Steven Jackson will be the cream of the 2013 free-agent running back crop if he declines his $7 million player option. Jackson has until March 12 -- the first day of free agency -- to decide. It's been expected that S-Jax will indeed decline the option, though it's always possible Jackson and his agent will determine they wouldn't pull in more money on the open market. I'd probably set Jackson's chances of returning to St. Louis at 55:45. If he doesn't, expect Atlanta and Green Bay to be among the contenders that pursue him. At age 29, Jackson has plenty left in the tank.

There's a steep falloff behind him.

Reggie Bush, 27, is best suited for a complementary, third-down type role in a pass-first offense, ideally playing in a dome. The pass-happy Lions make a lot of sense as a suitor, assuming Bush's price tag is reasonable. Rashard Mendenhall, 25, has talent to be an NFL feature back, but his health has been unreliable the past two seasons and Mendenhall is maddeningly inconsistent on inside runs, too often bouncing outside. Released by the Giants, 26-year-old Ahmad Bradshaw suffers from chronic foot injuries and is much too brittle for any team to count on as a starter. He'll be viewed as a potential committee back or strict backup by clubs in the market for running backs. Cedric Benson, 30, is coming off a Lisfranc fracture. Bernard Scott, 29, returns from a torn ACL.

Another thin free-agent position, guard offers five or six NFL starters with two or three who might command big money should they hit the market. Athletic Andy Levitre, 26, has never missed a start in four seasons with Buffalo and was a top-ten guard in 2012 per Pro Football Focus' ratings. The Bills need to make re-signing Levitre a priority.

Donald Thomas, 27, can play all three interior line positions and held up well in seven 2012 starts. Brandon Moore, 32, is limited to right guard but is still blocking at a high level. Louis Vasquez, 25, is well regarded around the NFL and after Levitre may be the likeliest guard to receive a lucrative, long-term deal. Lance Louis, 27, Geoff Schwartz, 26, and Chad Rinehart, 27, are young guards with potential.

12. Fullback

Jerome Felton, 26 brings little to the table as a ball carrier or receiver, but he was the NFL's premier lead blocker in 2012 and deserved first-team All-Pro recognition over Baltimore's Vonta Leach. Fullbacks historically have short shelf lives and ought to max out their market whenever possible. If Felton and his agent are smart, they will prioritize testing free agency unless the Vikings blow their socks off with a contract offer before March 12.

Greg Jones, 31, is the only other fullback who might generate serious free-agent interest. Jones is getting up there in age, but he's still a pile-driving run blocker and also excels in blitz pickup.

13. Inside Linebacker

I haven't studied up much yet on this year's draft-eligible inside linebacker class. But if it isn't stocked with talent, your team is in trouble if it needs a starter inside. Rey Maualuga, 26, is a poor starter and he's among the best free agency can offer. Brian Urlacher's 34-year-old knees are shot. Tim Dobbins, 30, is a major liability in coverage. Dannell Ellerbe, 27, is a candidate to get overpaid on the heels of his team's Super Bowl win.

Perhaps the one free agent inside linebacker worth the longest look for needy teams is Brad Jones, a 26-year-old converted pass rusher who more than adequately replaced D.J. Smith for the Packers in 2012. Jones started ten games and outplayed A.J. Hawk. Teams still figure to be wary of Jones because his experience inside is so limited.

14. Center

There isn't a free-agent center who'll be viewed as a surefire starter. Todd McClure, 36, Brad Meester, 35, and Dan Koppen, 33, are all nearing retirement. And they're the best there is in this year's center class.

15. Quarterback

With Flacco a virtual lock to return to Baltimore, quarterback is another position that lacks a single bankable starter. Matt Moore, 28, comes the closest after losing the Dolphins' starting job to Ryan Tannehill last summer. Moore will probably wind up in a camp battle on a quarterback-desperate team like the Jets, Cardinals, Jaguars, or Bills.